Computer systems contain large amounts of information. This information includes personal information, such as financial information, customer/client/patient contact information, business information, audio/visual information, and much more. This information also includes information related to the correct operation of the computer system, such as operating system files, application files, user settings, and so on. With the increased reliance on computer systems to store critical information, the importance of protecting information has grown. Traditional storage systems receive an identification of a file to protect, and then create one or more secondary copies, such as backup files, containing the contents of the file. These secondary copies can then later be used to restore the original data should anything happen to the original data.
In corporate environments, protecting information is generally part of a routine process that information technologists perform for many computer systems within an organization. For example, a company might back up critical computing systems related to e-commerce such as databases, file servers, web servers, and so on as part of a daily, weekly, or monthly maintenance schedule. The company may also protect computing systems used by each of its employees, such as those used by an accounting department, marketing department, engineering department, and so forth.
Continuous data protection (CDP), also sometimes called continuous data replication (CDR) or continuous backup, refers to protecting computer data by automatically saving a copy of every change made to that data, essentially capturing every version of the data that a user or process saves. CDP allows the user or an administrator to restore data to any point in time, at the point of any change. There are multiple methods known in the art for capturing the continuous changes involving different technologies that serve different needs. CDP-based solutions can provide fine granularities of restorable objects ranging from disk images to logical data objects such as files, mailboxes, messages, database files, and database logs. CDP is different from traditional backup in that it is not necessary to specify the point in time to which to recover data until a restore is about to be performed. Traditional backups can only restore data to the point at which the backup was taken. With CDP, there are no backup schedules. When data is written to disk, it is also asynchronously written to a second location, usually another computer over the network. In many situations, CDP requires less space on backup media (e.g., disk or tape) than traditional backup. Most CDP solutions save byte or block-level differences rather than file-level differences. This means that if a change is made to one byte of a 100 GB file, only the changed byte or block is backed up, whereas traditional incremental and differential backups make copies of entire files when those files change.
CDP typically relies upon a highly reliable, continuous connection between the computer system containing data to be protected and the data storage system so that each change to data can be replicated between the computer system and the data storage system when it happens. However, many computers in an organization are not continuously connected, but still contain important data that needs protection. For example, laptops, cell phones, tablet PCs, smart appliances, and other types of portable computer systems may only be connected to the network once a day or once a week, such as after a business trip or when the user is at a wireless hot spot. Even when these computer systems are connected, CDP is often a poor choice for protecting data because the input/output (I/O) performance for constantly replicating writes from these devices is very bad. Typically, such computer systems are either not protected or are protected through slower or less convenient data protection technologies, such as disk imaging, traditional full or incremental backups, and so forth. The use of different types of data protection throughout an organization leads to additional administrative burden for already overloaded information technology (IT) personnel and resources.
The foregoing examples of some existing limitations are intended to be illustrative and not exclusive. Other limitations will become apparent to those of skill in the art upon a reading of the Detailed Description below. These and other problems exist with respect to data storage management systems.
In the drawings, the same reference numbers and acronyms identify elements or acts with the same or similar functionality for ease of understanding and convenience. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 100 is first introduced and discussed with respect to FIG. 1).